This invention relates to acyclic machines, and, more particularly, to such machines utilizing liquid metal current collectors for completing electrical connection between the relatively rotating rotor and stator members thereof. Such machines include the disk type acyclic machine as described in U.S. Pat. No. 3,585,398, issued June 15, 1971 to L. M. Harvey and assigned to the instant assignee, a disk/drum type acyclic machine as disclosed in my U.S. patent application Ser. No. 898,923, filed Apr. 21, 1978, now U.S. Pat. No. 4,208,600, and assigned to the instant assignee, and drum-type acyclic machines.
For high current density operation of acyclic machines, such as those employing superconducting field coils, it is necessary to provide a reliable high current-carrying capacity contact between rotor and stator members. In machines using liquid metal current collectors, this requires a constant reliable supply of liquid metal to the current collectors in order to continuously wet the contact surfaces and bridge the gap between the relatively rotating rotor and stator members. In a disk-type machine operating at high speed, centrifugal force tends to drive the liquid metal from the radially-inner current collectors. For both drum-type and disk-type machines operating at high speed, Lorentz expulsion forces tend to expel the liquid metal from the collectors. If the liquid metal is expelled from the current collectors, the collectors will run dry, in which condition the current collectors lack adequate current-carrying capacity to transmit the high current density produced in such machines, and arcing between current-carrying members may occur. Severe damage to the current-carrying contact surfaces of the relatively moving current collectors would quickly follow.
One approach to maintaining adequate liquid metal in the current collectors in high speed acyclic machines is described in my U.S. Pat. No. 4,027,183, issued May 31, 1977, and assigned to the instant assignee and in U.S. Pat. No. 4,027,184, issued May 31, 1977 to Hurley and assigned to the instant assignee. Each of these patents is drawn to localized circulation of liquid metal around a single current collector, which requires a large quantity of liquid metal in the gap separating the stator and the rotor. The relatively large quantity of liquid metal required for these current collectors creates relatively large viscous losses due to frictional contact between the rotor surfaces moving relative to the liquid metal in contact with the rotor, reducing machine efficiency.
In my earlier-filed U.S. patent application Ser. No. 924,055, filed July 12, 1978, now U.S. Pat. No. 4,207,486, and assigned to the instant assignee, a technique for producing liquid metal circulation within an acyclic machine is described, in which kinetic energy is imparted to liquid metal within the current collector by the rotating rotor collector ring. A scoop collects a portion of the circulating liquid metal, converts the kinetic energy into pressure, and supplies a pressurized flow of liquid metal through passages in each stator disk to a radially-inner current collector from a radially-outer current collector. A return flow path is provided within each stator disk to maintain continuous circulation of liquid metal between adjacent radially-inner and radially-outer current collectors.
In my prior-filed U.S. patent application Ser. No. 58,220, filed July 16, 1979, assigned to the instant assignee, and incorporated herein my reference thereto, a liquid metal current collector configuration is described which employs the integral electromagnetic pump concept to circulate liquid metal circumferentially about a pump groove within the stator disk to supply a continuous source of liquid metal around the current collector without requiring external machinery to pressurize the liquid metal. The pump groove was disposed in a stator collector ring so that a continuous supply of liquid metal could be provided to both inner and outer collector rings of a disk-type acyclic machine.